In recent years, the ink jet technology has been expected for use as manufacturing apparatuses, not merely as printer devices for forming images on paper mediums. For example, in JP 2003-84125 A or JP 2003-127392 A, an apparatus construction in which droplet ejecting elements using the ink jet system are mounted is disclosed as a manufacturing apparatus for liquid crystal displays, organic EL displays and the like.
A general-use printer by the ink jet system, typically, forms images by using a droplet ejecting section as one ink jet head unit on which several pieces of ink jet head elements each having a width of ½ to 2 inches and having nozzle openings regularly arrayed at intervals of 150 to 300 nozzles/inch are mounted as elements for ejecting droplets in some plural quantity for each of the individual colors. As the method therefor, it has been practiced that recording sheet, while fed by a sheet feed roller, is scanned a plurality of times in a direction perpendicular to the carrying direction of the recording sheet so that an image is formed on the recording sheet.
Even with the use of the ink jet system as a manufacturing apparatus, the ink jet head elements are similar to those of general-purpose printers, the size of each ink jet head element in the nozzle array direction being 1 to 2 inches at most as it stands.
Meanwhile, manufacturing processes for liquid crystal displays, organic EL displays and the like are increasingly directed toward increasing the yield quantity by using larger-area substrates to reduce the cost and the cycle time. Manufacture of these devices and others by the ink jet system, it has been considered, would require an apparatus that is capable of managing large-area substrates having one side as much as several meters.
In JP 2003-84125 A or JP 2003-127392 A, a plurality of droplet ejecting sections (heads) are used to meet such large-area substrates as described above.
In another aspect, if there are variations in the distance (hereinafter, referred to as a gap of a droplet ejecting section) from each of droplet ejecting surfaces of the droplet ejecting sections to a surface of an objective substrate, then the time elapsing from ejection to landing is varied, causing the landing position to be varied. Therefore, it is necessary to adjust the gaps of the droplet ejecting sections so that all the droplet ejecting sections become generally equal in gaps. These droplet ejecting sections need replacement due to damage of the droplet ejecting surfaces, internal solid sticking or the like, which gives rise to a need for adjustment of gaps of the droplet ejecting sections on each replacement of the droplet ejecting sections.
As a method for adjusting the gaps of the droplet ejecting sections, JP 2005-31144 A discloses a technique using a distance measuring device.
In JP 2005-31144 A, one distance measuring device is used to perform the gap adjustment of droplet ejecting sections with respect to a plurality of droplet ejecting sections. In this case, the droplet ejecting sections, each having one or a plurality of ejecting elements and a housing for housing the ejecting elements therein, are fittable and removable in block.
Moving the distance measuring device between the plurality of droplet ejecting sections would cause the distance measuring device to be incorrect in height. As a method for correcting the incorrect height of the distance measuring device, JP 2005-31144 A discloses a technique that a reference surface is provided within a substrate-mounting stage to correct the height of the distance measuring device.
Also, whereas the adjustment of the gaps of the droplet ejecting sections is necessarily required after the fitting of the droplet ejecting sections, the gaps of the droplet ejecting sections are normally as narrow as about 0.5 mm. Therefore, it is necessary to make the stage escape from under the droplet ejecting sections during the time duration from the fitting of the droplet ejecting sections until the adjustment completion of the gaps of the droplet ejecting sections.
The procedure for adjustment of the gaps of the droplet ejecting sections is now explained. First, the distance measuring device is moved to under the droplet ejecting sections, and the stage is moved to under the droplet ejecting sections, in which state the correction of the distance measuring device is carried out. Thereafter, the stage is made to escape from under the droplet ejecting sections, and old droplet ejecting sections, if any, are removed and new ones are fitted, followed by executing the gap adjustment of the droplet ejecting sections.
However, with the technique disclosed in JP 2005-31144 A, the moving distance of the stage is increased with increasing size of the substrate, taking longer time for the movement of the stage. This would result in increases in the time for replacement of the droplet ejecting sections heretofore. Also, increases in the size of the substrate would lead to increases in size of the stage, causing an increase in cost as well as an increase in size of the apparatus as a whole.
With regard to the stage, if not a movable stage but a stationary stage is used, the distance measuring device, which needs to be subjected to height adjustment as it is under the droplet ejecting sections, cannot be subjected to height correction by using the stationary stage because the replacement of the droplet ejecting sections needs to be done at places away from the stationary stage.